FARO, Portugal — Jaguar is weeks from launching the battery-electric I-Pace crossover, the first EV challenger from a mainstream automaker to Tesla's Model X.
The I-Pace, under development for four years, has many parts and systems that Jaguar Land Rover perfected in-house. The twin electric motors are part of a patented JLR design that has a driveshaft that runs through the motors and bolts to the wheels.
Simon Patel, JLR's senior manager of battery-electric vehicle propulsion, spoke with Staff Reporter Richard Truett about the I-Pace's technical details during an introductory event for the vehicle here.
Q: Did JLR engineers do all the calibrations for the electric motors, battery pack and power electronics in-house?
A: All of the calibration is done in-house by Jaguar engineers, including the batteries — and it was a lot of hard work. The vehicle supervisory controller houses the powertrain control module, and the software for that was written in-house over the last five years. It is modular software that is capable of full electric, mild hybrids and plug-in hybrids such as the Range Rover plug-in hybrid that was released last year.
JLR has been involved in Formula E racing for a couple of seasons. Has anything the company learned from racing electric cars gone into the I-Pace?
Not in terms of direct technology. We had the concept of the basic layout of the batteries and electric motors set four years ago, before Formula E came about. But we have people embedded on the Formula E team so we have that cross-pollination of ideas. And concepts around how software operates have slightly gone into the car, but there is no one thing from Formula E in the I-Pace.
The I-Pace has an electric motor on the front and rear axles. When it is driving on the road at 70 mph, do both motors drive all four wheels?
We've calibrated motors to be operating at their most efficient at all times. Generally, that's splitting the load between the two motors. At very low speeds, sub-30 mph with very light loads, we turn off the front, so it's a rear-wheel-drive car. But as soon as you get over 30 mph, the front motor will come in. Or, if you do any more than feathering the throttle, the front will come in. As soon as you are over 30 mph, it's fundamentally a 50-50 split that we operate.
What about the electric drivetrain components?
The inverter has been developed specifically for us. It has some very high tech IGBTs (semi-conductors) capable of operating at 550 amps. The real clever bits are the motors, permanent magnet machines, that were developed in-house.
The front and rear motors are exactly the same, and so is the epicyclic gear set and differentials. The only difference between front and rear is the external casing because they have different mounting points.
With the battery pack between the frame rails, what happens in a hard side-impact collision?
The car will pass all crash standards to a very high level. But one of the biggest issues for a battery-electric car is side-impact. The pack comes right to the inside of the sill. Within the side of the pack there is a large aluminum extrusion. And that has been designed in conjunction with the body to act as one in a crash.
Computer-aided design suggested that when there is a side-impact collision, there might be slight indentation on the inside of the battery pack. But in crash tests, we were pleased to open the pack and not see a mark on any of the modules. So the body and the extrusions and the side of the pack exceeded our expectations.
The I-Pace uses coolant to control the battery pack temperature year-round. How does that work?
The lithium ion battery pack has 432 pouch cells with 12 cells in each that make up 36 modules. Heat is drawn out of each module through the bottom of the pack, which is cooled with the air conditioning system. The whole bottom of the battery pack plate is cooled. In the winter, the coolant is heated with a positive temperature coefficient heater. That's basically a heating element that we turn on to warm up the coolant. The ideal temperature range of the pack is between 68 and 86 Fahrenheit. It can go below and above, but we try to keep the pack in that ideal region.
What was hardest about getting the systems to work smoothly?
Software is always a big challenge in getting everything to work harmoniously together — especially when there are so many different modules, sometimes from different suppliers. Charging has been a really big challenge for us, in terms of compatibility with everybody's DC charging station.
There are SAE standards that say how protocols should work. But because no one has really tested them too much yet, we implemented it and found that charger suppliers have implanted it slightly differently. And it's because the wording is quite loose. And there are over 30 different optional messages you can transmit and receive, and if the charge station is asking for a certain one and you don't give it back, the charger might not work.
It's been a real challenge to go around, physically testing every single charge station. When they don't work, you get in touch with the company and have a discussion to figure out to make it work. That might mean a change in software, sometimes on both sides, to make it compatible.
Were there any other major challenges?
Noise, vibration and harshness. We know what do to with an engine and a transmission and how to tune them. But in an electric vehicle, the frequency range is completely different. We've learned a hell of a lot with electric drive units. We've got double isolation in the front and the rear, two sets of rubber, and each one is set to tune out different frequencies. We've also got NVH jackets around the [electronic control units] to prevent any airborne losses from entering the cabin.
What maintenance will the I-Pace require over the first five years of ownership, other than regular wear items such as tires and wiper blades?
We've got two coolant circuits, so topping up the coolant. You might need to check the air conditioning system and change the cabin air filter. In terms of the electronics and drive units, they're sealed for life. And the battery requires no maintenance, either.